Sleep apnea, left untreated for even a few days, can increase blood sugar and fat levels, stress hormones and blood pressure, according to a new study of sleeping subjects. A report of the study’s findings, published in the August issue of The Journal of Clinical Endocrinology & Metabolism, adds further support for the consistent use of continuous positive airway pressure (CPAP), a machine that increases air pressure in the throat to keep the airway open during sleep.

“This is one of the first studies to show real-time effects of sleep apnea on metabolism during the night,” says Jonathan Jun, M.D., assistant professor of medicine at the Johns Hopkins University School of Medicine and the paper’s senior author.